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Add code needed to unpack decoded message.

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git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6645 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke 2016-04-24 15:08:57 +00:00
parent e68674214c
commit 45ba25f6ed
1 changed files with 33 additions and 19 deletions
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50
lib/ldpcsim.f90
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@ -7,8 +7,8 @@ use, intrinsic :: iso_c_binding
use hashing
use packjt
character*22 msg,msgsent
integer*4 i4Msg6BitWords(12)
character*22 msg,msgsent,msgreceived
integer*4 i4Msg6BitWords(12),i4Dec6BitWords(12)
integer*1, target:: i1Msg8BitBytes(10) ! 72 bit msg + 8 bit hash
integer*1, target:: i1Dec8BitBytes(10) ! 72 bit msg + 8 bit hash
integer*1 i1hashdec
@ -22,8 +22,8 @@ equivalence (ihash,i1hash)
nargs=iargc()
if(nargs.ne.7) then
print*,'Usage: ldpcsim pchk/gen file prefix N K niter ndither #trials s '
print*,'eg: ldpcsim "128-80-peg-reg3" 128 80 10 1 1000 0.75'
print*,'Usage: ldpcsim <pchk file prefix > N K niter ndither #trials s '
print*,'eg: ldpcsim "/pathto/128-80-peg-reg3" 128 80 10 1 1000 0.75'
return
endif
call getarg(1,prefix)
@ -54,7 +54,7 @@ allocate ( codeword(N), decoded(K), message(K) )
allocate ( lratio(N), rxdata(N) )
call init_ldpc(trim(pchk_file)//char(0),trim(gen_file)//char(0))
msg="K1JT K9AN EN50"
msg="123"
call fmtmsg(msg,iz)
call packmsg(msg,i4Msg6BitWords,itype)
call unpackmsg(i4Msg6BitWords,msgsent)
@ -104,19 +104,19 @@ do idb = 0, 11
do itrial=1, ntrials
! create a realization of a noisy received word
! Create a realization of a noisy received word
do i=1,N
rxdata(i) = 2.0*(codeword(i)-0.5) + sigma*gran()
enddo
! correct signal normalization is important for this decoder.
! Correct signal normalization is important for this decoder.
rxav=sum(rxdata)/N
rx2av=sum(rxdata*rxdata)/N
rxsig=sqrt(rx2av-rxav*rxav)
rxdata=rxdata/rxsig
! To match the metric to the channel, s should be set to the noise standard deviation.
! For now we just set s to the value that optimizes decode probability near threshold.
! For now, set s to the value that optimizes decode probability near threshold.
! The s parameter can be tuned to trade a few tenth's dB of threshold for an order of
! magnitude in UER
do i=1,N
@ -128,18 +128,16 @@ do idb = 0, 11
lratio(i)=exp(2.0*rxdata(i)/(ss*ss))
enddo
! call interface to Radford Neal implementation of binary belief propagation.
! max_iterations is max number of belief propagation iterations
! max_dither is the number of tries - try number 2 and beyond start with dithered likelihood ratios.
call ldpc_decode(lratio, decoded, max_iterations, niterations, max_dither, ndither)
! if the decoder finds a valid codeword, niterations will be .ge. 0
! If the decoder finds a valid codeword, niterations will be .ge. 0.
if( niterations .ge. 0 ) then
nueflag=0
nhashflag=0
! the decoder produced a codeword --- compare hash part of message (byte 10) with computed hash
! first collapse 80 decoded bits to 10 bytes
! the first 9 bytes are the message, 10'th byte is the hash.
! The decoder found a codeword. Compare received hash (byte 10) with computed hash.
! Collapse 80 decoded bits to 10 bytes. Bytes 1-9 are the message, byte 10 is the hash.
do ibyte=1,10
itmp=0
do ibit=1,8
@ -147,17 +145,19 @@ do idb = 0, 11
enddo
i1Dec8BitBytes(ibyte)=itmp
enddo
! calculate the hash using the first 9 bytes
! Calculate the hash using the first 9 bytes.
ihashdec=nhash(c_loc(i1Dec8BitBytes),int(9,c_size_t),146)
ihashdec=2*iand(ihashdec,255)
! compare calculated hash with received byte 10 - if they agree, keep the message
! Compare calculated hash with received byte 10 - if they agree, keep the message.
i1hashdec=ihashdec
if( i1hashdec .ne. i1Dec8BitBytes(10) ) then
nbadhash=nbadhash+1
nhashflag=1
endif
! check the message plus hash against what was sent
! Check the message plus hash against what was sent.
do i=1,K
if( message(i) .ne. decoded(i) ) then
nueflag=1
@ -166,11 +166,25 @@ do idb = 0, 11
if( nhashflag .eq. 0 .and. nueflag .eq. 0 ) then
ngood=ngood+1
! don't bother to unpack while testing
if( .false. ) then
! unpack 72-bit message
do ibyte=1,12
itmp=0
do ibit=1,6
itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*6+ibit))
enddo
i4Dec6BitWords(ibyte)=itmp
enddo
call unpackmsg(i4Dec6BitWords,msgreceived)
print*,"Received ",msgreceived
endif
else if( nhashflag .eq. 0 .and. nueflag .eq. 1 ) then
nue=nue+1;
endif
endif
enddo
write(*,"(f4.1,1x,i8,1x,i8,1x,i8)") db,ngood,nue,nbadhash